Prawn – or is it shrimp? It really all depends on where you are. In some countries larger species are referred to as prawns and smaller species as shrimp. Other places, like the USA, have the differentiation the other way round. Some chefs and cookbooks say the difference is size. Small and medium shrimp are sold as, well, shrimp, while large or jumbo are sold as prawns. But this ‘rule’ doesn’t always hold! The Food and Agriculture Organisation of the United Nations has attempted to clear things up with definitions of its own. According to them, a shrimp is a saltwater crustacean and a prawn is a freshwater crustacean. I think they mean they’re basically the same! But given it is the United Nations, no one is going to listen to them anyway!

Regardless of what they are called, they adorn just about every menu in most countries. And, nowadays, they’re farmed and relatively inexpensive. They’re also particularly versatile, and can be deep-fried, battered, used in stir-fries, thrown into salads and sandwiches, chopped up and used in dips, tossed into curries or combined with other seafood. And on Samui you’ll find them displayed in restaurants as they are an integral part of the culinary scene. Quite rightly too, as Thailand is one of the biggest producers and exporters of shrimp in the world.

Marine (saltwater) shrimp have been farmed since the 1970s, and production has grown steeply to match the global market demands. In 2003, marine shrimp production reached more than 1.6 million tonnes, representing nearly 9 billion US dollars. And about 75% of it was produced in Asia, predominately in Thailand and China. Virtually all of these are of the family Penaeidae with just two species Penaeus monodon (giant tiger prawn) and Litopenaeus vannamei (pacific white shrimp) accounting for roughly 80% of all farmed marine shrimp.

Freshwater prawns on the other hand had a global production in 2003 of about 280,000 tonnes. China was responsible for some 180,000 tonnes followed by Thailand and India with 35,000 tonnes each. All of the farmed freshwater prawns today belong to the genus Macrobrachium. Until the year 2000, the only species farmed was Macrobrachium rosenbergii (giant river prawn). Since then, China has begun farming the oriental river prawn in large quantities, and India farms a small amount of monsoon river prawns..

In all there are around 200 species in the genus Macrobrachium and they occur throughout the tropics and subtropics, on all continents except Europe. And while the giant river prawns live in turbid freshwater, their larval stages require brackish water to survive. Males can reach a body size of 32cm and females can grow to 25cm. Typically, they will be harvested at around five months but that can depend on the conditions and technology utilised.

Farming of both saltwater and freshwater prawns basically uses the same technology. Hatcheries produce post-larvae, which are then grown and acclimated in nurseries before being transferred into grow-out ponds. They are then fed and grown until they reach marketable size. Harvesting is done by either draining the pond and collecting them, or by fishing the prawns out of the pond using nets. Due to the aggressive nature of giant river prawns and the hierarchy between males, stocking densities are much lower than in saltwater farms. Intensive farming is not possible due to increased levels of cannibalism.

Freshwater prawn farming is considered by the United Nations to have less of an ecological impact than saltwater farming. Prawns are cultured in the freshwater environment at much lower densities, meaning less concentrated waste products, and a lesser danger of the ponds becoming breeding grounds for disease. Grow-out ponds do not salinate agricultural land nor endanger mangroves. Additionally, freshwater farms are amenable to small-scale businesses run by a family. Another small business common in Thailand is the production of shrimp paste. Tiny shrimp caught off the coastal waters are made into blacang, a fermented paste that can take up to a year to mature. It’s used extensively in Thai cuisine and has an aroma unlike anything else. Needless to say, if you take some home with you, use it sparingly!

When choosing prawns for use at home consider what you want to do with them to get the best results. Warm and cold water prawns have different textures and can bring out different flavours. Warm water prawns tend to be slightly bigger and have a stronger taste, so are more suited to strong spicy dishes. Cold water prawns tend to be smaller and milder, ideal for salads and snacks.

No matter what you call them, they are delicious to eat in a myriad of ways. And don’t be overly concerned when they come shell-on, getting messy with food is one of the few legal pleasures that you can get away with in public here. Just try not to do as a friend of mine once did. After staring into the warm, lemon-scented finger bowl for a while he then complained that he hadn’t ordered the soup and, anyway, it was the thinnest, blandest broth he’d ever tasted!